As a backlight used for a liquid crystal display device, an edge-light type backlight is known. The edge-light type backlight introduces, from the side edge surface of a rectangular flat light guide plate, light emitted by a light source, and outputs it from the principal surface of the light guide plate. The edge-light type backlight is advantageous in terms of reducing the thickness of a housing, compared to a direct type backlight which includes a light source opposed to the back surface of a liquid crystal panel and directly illuminates the liquid crystal panel.
However, in an edge-light type backlight, a light source is arranged opposite to the side edge surface of a light guide plate, that is, a light source is accommodated in the frame part (i.e., bezel) of a housing, thus disadvantageously requiring a housing having a large frame part.